Morphology, Structure, and Ontogeny of Trichomes of the Grape Genus (Vitis, Vitaceae).

Zhi-Yao Ma,Long-Qing Chen,Xiu-Qun Liu,Jun Wen,Stefanie M Ickert-Bond

doi:10.3389/fpls.2016.00704

Abstract

Trichomes are widely distributed on surfaces of different organs in the grape genus Vitis and are of taxonomic utility. To explore the morphology, structure and ontogeny of Vitis trichomes, we investigated the diversity and distribution of trichomes in 34 species of Vitis. Two main types of trichomes in Vitis are documented: non-glandular and glandular. Within non-glandular trichomes, ribbon and simple trichomes are found on different vegetative plant organs. The morphology and ontogeny of these types of trichomes are further examined with light microscopy and scanning electron microscopy. The ultrastructure of the glandular trichomes is explored with transmission electron microscopy. The ribbon trichomes are twisted, greatly elongated and unicellular, and this trichome type may be a morphological synapomorphy of Vitis and its closest tropical relative Ampelocissus and Pterisanthes in Vitaceae. The simple trichomes are documented in most species sampled in the genus. The glandular trichomes are multicellular, non-vascularized and composed of both epidermis and subjacent layers. We show that prickles occurring along the stems and petioles of Vitis davidii are modified glandular trichomes. We observed that glandular trichomes of V. romanetii secrete mucilage and volatile substances which trap insectes on the glands. Transmission electron microscopy indicates that metabolic products accumulate in vacuoles, the cytoplasm and intercellular spaces. We infer that glandular trichomes and young prickles are involved in the secretion of these metabolic products and the intercellular spaces may be the places of temporary storage of these secretions.

Highlights

Trichomes usually originate from epidermal cells and are ubiquitous in many plant families, showing great diversity in morphology, cellular structure and function (Uphof, 1962)
Ribbon trichomes can be as long as several millimeters
On the abaxial leaf surfaces, ribbon trichomes are found in 26 species, of which 11 species have non-deciduous dense arachnoid indumentum composed of this trichome type (Figure 1B; Table 1; V. adenoclada, V. bellula var. pubigera, V. heyneana, V. heyneana subsp. ficifolia, V. hui, V. lanceolatifoliosa, V. retordii, V. sinocinerea, V. labrusca, V. mustangensis, and V. shutterworthii)

Summary

Introduction

Trichomes usually originate from epidermal cells and are ubiquitous in many plant families, showing great diversity in morphology, cellular structure and function (Uphof, 1962). These epidermal appendages are unicellular or multicellular, branched or unbranched, glandular or non-glandular (Levin, 1973; Werker, 2000; Yang and Ye, 2013). Grapes have been widely recognized for their agronomic and economic importance as fresh fruits, and sources of wine and raisins (Wen, 2007). Other species of the grape genus (Vitis L.) are important germplasm resources for the wine grape (V. vinifera L.), and have been bred to improve resistance of cultivated varieties against many fungal diseases and to enhance cold tolerance (Staudt and Kassemeyer, 1995; Wang et al, 1995; Staudt, 1997; Brown et al, 1999; Wan et al, 2007; Zhang et al, 2012; Gerrath et al, 2015)

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